Pension Plans, Retirement Benefits and Savings Plans (details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 30	$ 32	$ 59	$ 65
Interest cost on benefit obligation	31	36	61	72
Expected return on plan assets	(58)	(57)	(115)	(115)
Net periodic benefit cost, settlement	1		1
Net periodic benefit cost, amortization of unrecognized net actuarial loss	16	24	33	48
Net periodic benefit cost	20	35	39	70
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Interest cost on benefit obligation	2	2	4	5
Net periodic benefit cost, amortization of unrecognized prior service benefit	(1)		(2)	(1)
Net periodic benefit cost	$ 1	$ 2	$ 2	$ 4